Empathy is also at work in apes, reports Roger Highfield

When an orangutan laughs, his friends laugh along too. The discovery that our relatives have good moods that are contagious suggests that empathy, a key aspect of being human, was born at least 12 million years ago.

When we smile at friends they smile back. The same goes for yawns and this kind of mimicry – what scientists call “emotional contagion” – forms an aspect of empathy that allows us to experience the emotions of others.

Despite evidence that yawns are as infectious to apes and monkeys as they are to humans, there has been no other evidence of this at work to spread other emotions in animals. Now emotional contagion has been shown to be at work in primates for the first time in a study by Dr. Marina Davila-Ross, University of Portsmouth, conducted with Prof. Elke Zimmermann at Institute of Zoology, University of Veterinary Medicine Hannover, and Centre for Systems Neuroscience, Hannover, published in the journal Biology Letters.

They studied the way facial expressions were picked up and imitated by 25 orangutans during everyday play at Sepilok Rehabilitation Centre, Apenheul Primate Park, Tierpark Carl Hagenbeck and Leipzig Zoo.

The team focused on an open mouthed expression which is the orangutan’s equivalent of human laughter and found that it was reciprocated so quickly that the apes had no time to think about it. “Results clearly indicated that orangutans mimic open-mouth faces of their playmates within 0.4 second, which confirms rapid involuntary facial mimicry in nonhuman mammals,” they report.

Thus the human phrase “laugh and the whole world laughs with you” goes as much for orangutans as humans. However, not every ape would smile back and this may reflect social factors familiar to humans: they were more clearly returning the smiles of friends than strangers. This suggests that this attribute, a building block of emotional contagion, predates humans by many millions of years, since we share a common ancestor with orangutans some 12-16 million years ago.